This invention relates to range hoods, and more particularly to a make-up air device for a range hood.
A typical exhaust hood for a cooking range includes an exhaust plenum mounted over the range and an exhaust fan for drawing air containing grease, vapor, smoke, and other particulates upward away from the range and out of the cooking area. Of course, when the foul air is withdrawn from the cooking area, it must be replaced by make-up air from another source. Generally, in commercial kitchens, such as in restaurants and institutions, the make-up air is quite frequently brought into the cooking area from the outdoors, sometimes through a supply air plenum including a single register having restricted openings. A make-up or supply fan may force air into the supply air plenum, and/or the air may be drawn across the range by the suction from the exhaust fan.
However, in spite of the efforts to restrict the supply air flow adjacent the cooking range, because of the minimal control of the direction of the supply air, inevitably a substantial amount of make-up air is drawn from the space within the cooking area or kitchen, thereby disturbing the equilibrium of the conditioned air within the cooking air. In the winter time, the kitchen area will tend to be cooled by the withdrawal of the normally heated air through the exhaust hood, and in the summer, the cool conditioned air within the kitchen will also be drawn through the exhaust hood, creating an extra energy demand upon the heating and cooling equipment for the kitchen area.
Moreover, in prior make-up air systems, the supply air, because of its high velocity and lack of direction, frequently creates a draft upon the cooks to their discomfort and sometimes ill-health.
The supply air registers conventionally used have a restricted air flow because of their small free area. Thus, the velocity of the air has to be increased in order to adequately ventilate the area over the cooking range, and consequently produces the undesirable drafts.
Some make-up air systems include perforated plates above the air discharge slot from the supply air plenum, but have no volume or velocity control.
Discharge louvers have been utilized as optional features in the discharge slot of some make-up systems for a range hood in order to control the direction of the air, but have not been utilized in combination with means for controlling the volume of air as well.
Even in prior art make-up air systems which employ registers, perforated plates, or discharge louvers, narrow jets of high velocity air still flow through at least some of the discharge openings because of the increase in fluid velocities generated by the sudden expansion of air flowing from the supply duct into the plenum from which the air is discharged.